With Fox News due to announce Tuesday which candidates will be onstage for the first debate of the GOP primary season, the fight for the final slot is a battle of governors -- Rick Perry versus Chris Christie, and the Texan appears to be losing.

The GOP has 17 candidates who have announced that they're seeking the nomination, so debate sponsors have to find some way to cull the field. Fox, the broadcast sponsor for Thursday's session, announced in the spring that 10 candidates would get to debate, picked based on who has the highest average standings in the five most recent national polls released by Tuesday.

So far, the most recent polls, including one released Monday evening by Fox, all tell pretty much the same story: Donald Trump in the lead, followed by former Florida Gov. Jeb Bush and current Wisconsin Gov. Scott Walker.

After those three, the recent polls show five other candidates bunched fairly tightly, all getting support in the mid- to high single digits -- Sens. Ted Cruz of Texas, Rand Paul of Kentucky and Marco Rubio of Florida, along with former Arkansas Gov. Mike Huckabee and Ben Carson, the retired neurosurgeon.

The Times' Seema Mehta has a preview of tonight's Republican candidate forum sponsored by the New Hampshire Union Leader.

The lineup won't be as complete as Thursday's prime-time debate. Donald Trump declined an invitation after the newspaper's editorial page ran a critical editorial.

Still, the forum will act as something of a dry run ahead of that first debate. For some candidates, it may be the most attention they get all week.

The first presidential debate of the 2016 election is Thursday. Compare the résumés of the crowded field of Republican and Democratic presidential hopefuls.

How do you debate Donald Trump?

Do you?

The real-estate tycoon, reality television star and now GOP presidential hopeful is a puzzle to observers of the 2016 campaign. In stump speeches, he often goes off on tangents about illegal immigration and overseas business deals, and jabs at politicians on both sides of the aisle.

The Times' Kurtis Lee and Seema Mehta asked some campaign experts.

Engage.

“It is different for every candidate. If I were advising a third-tier candidate I might engage in order to borrow some of the spotlight the media has trained on Trump, especially to sound like a strong, reasonable voice by comparison.

“If I were advising a top-tier candidate, I would advise ignoring him and communicating your own message. As my boyfriend, who grew up on a ranch, says: 'Never wrestle a pig. You just end up getting dirty and making the pig mad.'

“That said, in a debate, the top-tier candidates need to be prepared for crazy attacks from Trump and need to be ready to respond with strength and poise.”

- Katie Packer Gage, deputy campaign manager to 2012 Republican presidential nominee Mitt Romney

Focus on your message.

“Trump doesn't need anyone else's help to get attention or headlines. The governor [candidate Mike Huckabee of Arkansas] is going into this with the sole focus of using his time to get his message out, show the contrast and also display his personality and connect with people from the stage.”

- Alice Stewart, communications director for former Arkansas Gov. Mike Huckabee

Jeb Bush endorses a crackdown on sanctuary cities, an e-Verify system and border fencing as "a component" of the improved security measures he says will cut back on illegal immigration.

Bush outlined his six-point plan for border security in a post on Medium on Monday morning. and his campaign gave New Hampshire's WMUR a look in advance.

Hillary Rodham Clinton will spend $2 million over the next five weeks on television ads in New Hampshire and Iowa, the Times' Evan Halper reports.

"The ads are what is to be expected from a front-runner. Safe, biographical, nonconfrontational. But the placement of them is clearly intended to put challengers on notice," Halper writes.

Can a focus on fetal issue research change minds about abortion rights?

That's the question Republicans are testing as they forge ahead with their push to cut off federal money for Planned Parenthood amid accusations that the group profits off sales of tissue for research.

The Senate is slated to vote Monday on a measure. Republicans pushing for the vote say they think the issue has traction with Democrats.

"I think there are some pro-choice Democrats -- there are many pro-choice Americans -- who are horrified by this," Rand Paul told Fox's Sean Hannity.

Calling Islamic State militants the "greatest national security threat" to the country, Jeb Bush on Sunday previewed a foreign policy speech he'll deliver at the Reagan Presidential Library next week.

"When you hear the president speak, the only time he's admitted a mistake that I am aware of is that he's said twice in the last year that we don't have a strategy as it relates to ISIS," said Bush, using an acronym for the group that wants to establish an Islamic caliphate in the Mideast.

"This is the greatest national security threat that we face," Bush told wealthy donors at a retreat in Dana Point organized by the Koch brothers.

Islamic State, which has recruited heavily in the United States and Europe, is "gaining energy," he said.

His Reagan Library speech will "relate to how we take out ISIS," Bush said. "It will have broader implications, because we can't do this alone. We have to do this in concert with our allies; we have to do this in a way that sustains it over the long haul."

The threat of homegrown terrorism should create a debate within the GOP about the role the U.S. government should play, he said.

"Should we have metadata programs? Can we protect civil liberties and also protect the homeland?" Bush said. "How do we identify these isolated cells of people in our country that hate America, that want to destroy us, that want to undermine our economy and freeze us in place? I think it's a real threat."

One of Bush's rivals for the GOP presidential nomination, Sen. Rand Paul of Kentucky, led a 10½ hour filibuster to protest renewal of the National Security Agency's domestic surveillance authority. The maneuver temporarily prevented the NSA from accessing Americans' telephone records, which critics say put the country at risk.