A key test of Donald Trump's campaign strength will undoubtedly be his ability to draw new voters, not just to his rallies, but to the polls in key contests.
Iowa is of particular interest, because it votes first and its caucus system is a little quirky.
One way to check how well the Trump organization is doing with new voters is to check with the state to see if voter registration is ticking up as the February 1 contest draws closer.
But Julie Pace of The Associated Press cautions those numbers might not paint a full or fair picture -- because Iowa allows same-day voter registration.
"It's a lot easier to get people who haven't participated before to participate once, as opposed taking two different steps," said Pace. "So the thing they're looking at is how slow the results come in on caucus night. If the results are coming in very slowly, they'll assume that more people are registering that night and that could be a good night for Mr. Trump."
2. A test for Cruz and his 'birther' response
Ted Cruz and his campaign say questions about his eligibility to be president are nonsense.
But Trump is stirring those questions, big time, and the senator from Texas has been forced to respond.
Over the weekend, the Cruz campaign produced a one-page memo making its case that there is no "birther" debate here. Among other things, it notes Cruz's mother was born in Delaware and was never a Canadian citizen, even though Cruz was born in Canada.
Will the Cruz campaign response be enough? Jonathan Martin of The New York Times suggested keeping track of how the campaign handles this in the week ahead will be instructive: "He relishes being the sort of whipping boy of the Washington establishment, but now the person going after him is far from the establishment."
Martin adds, "This is a really fascinating test for Cruz. I'm curious to see if those kind of talking points wind up ... in some kind of a paid media mail piece in Iowa."
3. Paul may soon face a tough choice
Rand Paul is struggling in the GOP presidential race and could soon face a tough choice.
His Senate seat is also on the ballot this year, and while Kentucky is generally a reliable red state, there is some concern back home that Paul's national ambitions have given Democrats a better chance than they might have in a normal year.
So CNN's Manu Raju says the calendar is worth watching for keys to Paul's thinking.
"It will be interesting to see who else gets in that race," said Raju. "That will be very instructive in telling us when Rand will get out of the presidential race."
"If he has a tough race back home for Senate, maybe he gets out earlier than anticipated. March 6 is the big day for Rand Paul: That's when the Kentucky caucus is to choose a presidential nominee in that state."
4. The Sanders campaign takes a page from Trump's playbook
The Bernie Sanders campaign is hoping to benefit from recent attacks by the White House and Hillary Clinton on his gun record.
The Bernie camp's thinking: Perhaps it will generate a backlash from his supporters.
Maggie Haberman of The New York Times says Sanders is, in part, learning a lesson from Trump and trying to stoke the anti-establishment mood.
"Hillary Clinton has telegraphed very clearly she's going to keep hitting him hard on this," said Haberman. "This is going to be an issue in the debate. They believe they can get some kind of support from their followers that will inoculate them."
5. 'Fired Up' and ready to be a State of The Union special guest
Edith Childs was a key figure in the first Obama presidential campaign, starting the "Fired Up ... Ready to Go!" cheer at an early South Carolina rally long before it was a trademark campaign slogan.
She was on hand for the first Obama inauguration, and now will be a guest of the White House as the President delivers his final State of the Union address on Tuesday.
CNN visited Childs in South Carolina in 2009 for our first "State of The Union" program -- the Sunday before the Obama inauguration.
A look back at that conversation is both nostalgic and telling.
Childs is a wonderful storyteller, and she intrigued us with accounts of the KKK, and of being a precocious and stubborn young girl who took drinks from the "whites only" water fountain back in the days of segregation because the water in the "colored" fountain was never cold.
Reviewing our conversation this weekend, two things jumped out.
Childs could not contain her joy at the moment, and her admiration of then President-elect Obama. But she also said she was worried he didn't fully understand how hard it would be to deliver on his promises of dramatic change.
And while she voiced hope that having an African-American president might help get her closer to a giant goal -- to be judged just "as a person" and not by the color of her skin -- she was quick to add, "There are still those that are not going to change no matter what."