Lanhee Chen, Mitt Romney's policy director during the 2012 presidential contest, announced Monday that he has joined Sen. Marco Rubio's campaign as a senior advisor.

"Sen. Rubio has a great combination of policy chops, political ability and an incredibly compelling life story, all of which makes him a very exciting candidate for our party at this time," Chen said.

Chen announced the news on Hugh Hewitt's radio show Monday afternoon. He previously served as deputy campaign manager for Steve Poizner's 2010 gubernatorial run, deputy policy director during Romney's 2008 presidential campaign, and a policy advisor for President George W. Bush's 2004 reelection campaign.

Chen will continue working as a research fellow at the Hoover Institution at Stanford University as he advises Rubio's campaign.

As soon as President Obama touched down in Iowa on Monday, he saw a reminder of the state's critical role in American politics and in his own success: a Hampton Inn, a frequent stop during his two presidential campaigns.

"I must have stayed there like 100 days," he joked at the start of a town hall meeting in Des Moines. "I'm sure I've got some points or something. I could get a couple free nights."

Officially, Obama's visit to Iowa, the state that hosts the first presidential nominating contest, had nothing to do with 2016. He came to Iowa in just his second visit since his reelection to tout his administration's new effort to simplify applying for financial aid.

Referring to the grind of the campaign, Obama joked that he couldn't "imagine what kind of person would put themselves through something like this." But even as he promised to stay out of the political fray, the audience's questions kept him right in it.

One attendee asked which candidate had the best ideas on education. "I'm going to beg off this question. Right now, I'm going to try to stay out of the campaign season, partly because I can't keep track of all the candidates," he joked. But as he offered his thoughts on the importance of a well-funded education system, Obama could not help himself.

"If you hear a candidate say that the big problem with education is teachers, you should not vote for that person," he said. "I can't tell you who to vote for -- at least not right now. Later I will. But I can tell you who to vote against."

A young woman identifying herself as an intern for Hillary Rodham Clinton's campaign asked Obama about whether an idea from Sen. Bernie Sanders, Clinton's Democratic primary opponent, for free college tuition was practical or realistic. The president only referred to his own administration's plan for free community college tuition. "If we can get that done, then we can start building from there," he said.

Obama made perhaps his strongest political statement at the end, when asked whether people in the U.S. illegally would be eligible for the free community college plan.

He explained that existing law would make students who are undocumented ineligible for any federal loan programs. But he criticized those who he said don't welcome the desire of young immigrants to become "full-fledged parts of this community," saying it made "absolutely no sense."

"This whole anti-immigrant sentiment that's out there in our politics right now is contrary to who we are," he said. "Don't pretend that somehow 100 years ago the immigration process was all smooth and strict."

Obama never singled out any candidate as he criticized those who held those views. But he and his team are well aware of how Donald Trump has risen to the top of national polls in part because of his focus on stopping the flow of illegal immigration across the U.S.-Mexico border.

The president said the country could legitimately debate over how to reform the immigration system and said those who came to the U.S. illegally need to "get right with the law."

"We are treating new immigrants as if they're the problem -- when your grandparents were treated like the problem or your great-grandparents were treated like the problem or were somehow considered unworthy or uneducated or unwashed -- no! That's not who we are," he said. "I think that's un-American. I do not believe that. I think that is wrong. And I think that we should do better. Because that's how America was made."

With that, he thanked the audience and moved to shake hands as a Bruce Springsteen song began blaring from the loudspeakers. Just as it did so often in 2012.

Wisconsin Gov. Scott Walker became a favorite of conservatives when he took on the unions in his state.

Now slumping in the polls and looking for traction in his quest for the Republican presidential nomination, he wants to take his battle against unions to Washington.

Walker on Monday afternoon is set to deliver a speech on labor policy in Nevada calling for, among other things, more transparency from unions.

“I will hold unions accountable and require transparency of union expenditures,� said Walker, according to prepared remarks provided by the campaign. "On Day One, I will stop the big government union bosses from taking money out of the paychecks of federal employees for union dues spent on political activities.�

In Wisconsin, Walker was a staunch proponent of right-to-work legislation that he helped pass and sign into law that says workers cannot be forced to join labor unions, or pay union dues to keep a job.

While the move to curb collective bargaining gained plaudits from economic conservatives, it led to massive protests from Democrats and a 2011 recall effort. He ultimately survived the recall -- a major blow to unions in the state -- and ever since has championed himself as a battle-tested conservative ready to take the fight to big labor in ways that other candidates cannot.

“Our plan calls for national Right to Work. Specifically, we set a presumption that every employee in America -- public and private sector -- has the freedom to choose whether they want to be in a labor union or not,� says Walker, according to the prepared remarks. “This is pro-freedom and pro-worker.�

Walker's call to rein in labor unions drew a strong response from White House hopefuls vying for the Democratic nomination.

“At a time when the rich are getting richer and everyone else is getting poorer, Gov. Walker's attack on the trade union movement would lower wages and the benefits that working people receive while making the wealthy and large corporations even richer,� Sen. Bernie Sanders (I-Vt.) said in a statement.

When Walker announced his candidacy in July, he was considered a top contender for the party's nomination. But he has failed to gain much traction as GOP primary voters have offered support to outsider candidates -- billionaire businessman Donald Trump and retired neurosurgeon Ben Carson.

Expect Walker to highlight his plan to fight national labor unions when he takes the stage Wednesday night in Simi Valley for the second GOP presidential debate.

Carly Fiorina is hitting back at Donald Trump for insulting her appearance in a Rolling Stone magazine profile published last week.

A new Web ad released by her campaign doesn't mention Trump, but it riffs off his remarks as quoted in the magazine: "Look at that face!"

The back-and-forth all but guarantees that Trump will be forced again to talk about his comments about women at the GOP presidential debate scheduled for Wednesday.

Democratic presidential candidate Bernie Sanders tried to use his populist economic message to make common cause with his political opposites on Monday in a blunt speech to evangelicals.

Speaking at Liberty University, a Christian college founded by the late Rev. Jerry Falwell, Sanders argued that conservatives and progressives should be united in an effort to fight economic inequality.

The self-described socialist quoted Pope Francis' call for financial reforms and repeatedly cited scripture, including Amos 5: 24, saying “Let justice roll on like a river, righteousness like a never-failing stream.�

“Now when we talk about morality and when we talk about justice, we have to, in my view, understand that there is no justice when so few have so much and so many have so little,� he said. “In your hearts, you will have to determine the morality of that and the justice of that.�

Sanders spoke to a large audience that included many students and some of his boisterous supporters not affiliated with the school. While some in the crowd cheered his calls for government intervention on healthcare, paid leave and financial reform, many more reacted with moderate applause.

Sanders' speech was more likely to endear him to Democratic base voters -- who may be looking for a candidate willing to take risks and appear to take bold stands -- than to win over large numbers of conservatives.

He used the appearance to speak out against racism in the criminal justice system, praise President Obama as “a friend� and defend his positions on gay rights and abortion rights.

Sanders opened his remarks with a blunt declaration: “I believe in women's rights and the right of a woman to control her own body. I believe in gay rights and gay marriage. Those are my views and it is no secret."

"We disagree on those issues, I get that. But let me respectfully suggest that there are other issues out there that are of enormous consequence to our country -- and, in fact, to the entire world -- that maybe, just maybe we do not disagree on and maybe, just maybe we can try to work together to resolve them."

Journalists and pundits regularly default to boxing lingo on presidential debate nights, but CNN seems to be taking the metaphor a step further this week.

In promoting Wednesday's GOP primary debate, the network is hyping the event like it's a heavyweight bout, writes the Times' Stephen Battaglio, who quotes CNN President Jeff Zucker acknowledging "that was the idea."

Zucker isn't just relying on cliche. Wednesday's debate at the Ronald Reagan Presidential Library in Simi Valley, Calif. is shaping up to be slugfest. Candidates who spent last month's debate tiptoeing around Donald Trump have signaled they plan to come to blows this time. Meanwhile, Trump has started some new feuds in recent days, with comments that ensure Ben Carson and Carly Fiorina have reason to throw some punches.

All this potential for conflict has advertisers expecting big ratings.

"Strong demand for advertising time during the CNN debate has sent prices for a 30-second spot soaring into the $150,000-$200,000 range," Battaglio writes.

It was a busy weekend in presidential politics -- at least on the Republican side as candidates prepare to gather in Simi Valley on Wednesday for the Reagan Presidential Library debate.

Here are some highlights from the weekend:

> It kicked off with former Texas Gov. Rick Perry ending his presidential campaign. The move came after his failed 2012 bid for the Republican presidential nomination

> Drama between Donald Trump and Ben Carson continued. Both men, political neophytes, are polling at the top of the GOP presidential field. Trump, a billionaire businessman, offered a critique of Carson's candidacy Sunday

>Down in the polls, Jeb Bush has a strategy : compare his record as Florida governor to those of his rivals, such as Wisconsin Gov. Scott Walker and Ohio Gov. John Kasich