First Read is a morning briefing from Meet the Press and the NBC Political Unit on the day's most important political stories and why they matter.

The biggest impediment to stopping Trump right now is … John Kasich?

The Stop Trump movement is now picking up momentum with just a week to go until Super Tuesday (where 595 delegates are up for grabs on the Republican side). Yesterday, for instance, we saw more members of the GOP establishment -- Sen. Orrin Hatch, Sen. Dan Coats, Gov. Asa Hutchinson, Bob Dole -- endorse Marco Rubio. But maybe the biggest impediment to stopping Trump right now is … John Kasich. Think about it: If you assume that a big chunk of the Jeb Bush vote goes to Rubio, that means that Rubio can rack up delegates under the proportional allocation formulas. But Rubio won’t be able to grow his percentages as long as Kasich is in the race and competing in Super Tuesday states like Georgia (where he campaigns today), Tennessee (where he’ll be Friday and Saturday). And with Kasich in the race, it’s possible that Trump could sweep the Super Tuesday states a week from now – he’s in striking distance in Texas, where the University of Texas/Texas Tribune online poll has him trailing Ted Cruz there by just eight points (and that poll was taken before Saturday’s South Carolina results). If you’re the GOP establishment, the good news is the Quinnipiac poll showing Kasich losing to Trump in his home state of Ohio. The bad news: We’re just a week out from Super Tuesday, and it doesn’t look like Kasich is going anywhere anytime soon.

Don’t expect tonight’s results from Nevada until very late in the evening -- or even tomorrow

Today is the Nevada contest on the Republican side, but don’t expect to find out the results at a reasonable hour. Caucus-goers start gathering between 8:00 pm ET and 10:00 pm ET (submitting votes via paper ballot). All meetings end by midnight ET. In addition, the contest doesn’t have a history of being well run. Bottom line: We won’t know who wins until very late – even possibly tomorrow. And as a result, the winner won’t get the same kind of lift you’d see at an earlier time.

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Ted Cruz’s campaign picked a bad day to have a bad day

Firing a top communications aide just days after finishing third in South Carolina didn’t just produce a bad headline for the Cruz campaign yesterday; it also was an acknowledgement that the dirty tricks/lying narrative has become damaging. NBC’s Hallie Jackson from last night: “A startling shakeup for Ted Cruz, firing his top aide for tweeting this inaccurate video – wrongly suggesting Marco Rubio dismissed the Bible.” Said Cruz: “I had made clear in this campaign that we will conduct this campaign with the very highest standards of integrity… If other candidates chose to go into the gutter, we will not do the same.”

Sanders on the attack

“Just two days after losing to former Secretary of State Hillary Clinton in the Nevada caucuses, Senator Bernie Sanders launched a broadside against his rival, aggressively emphasizing differences between himself and Clinton on issues of campaign finance and trade policy,” NBC’s Danny Freeman reported. ‘What I intend to do over the next number of weeks is kind of contrast my record to Secretary Clinton's,’ Sanders began as he addressed the press at Boston's International Association of Ironworkers, Local 7. Keeping true to his word, the Vermont senator -- who boasts of having never run a negative campaign -- dove into a litany of contrast points he sees between himself and Clinton, launching some of the most direct swipes Sanders has taken at his competitor during this campaign season. ‘I am delighted that Secretary Clinton month after month seems to be adopting more and more of the positions that we have advocated, that's good,’ he said.”

Today’s polls

National online weekly NBC|SurveyMonkey tracking poll: Trump 36%, Cruz 19%, Rubio 16%, Kasich 8%, Carson 8%

National online weekly NBC|SurveyMonkey tracking poll: Clinton 51%, Sanders 40%

On the trail

Hillary Clinton campaigns in Columbia, SC… Bernie Sanders stumps in Norfolk, VA before heading to Columbia, SC, where he and Clinton participate in a CNN town hall at 9:00 pm ET… Donald Trump holds a rally in Sparks, NV at 3:00 pm ET… Ted Cruz also is in Nevada… Marco Rubio hits Nevada, Minnesota, and Michigan… And John Kasich stumps in Georgia.

Countdown to Dem South Carolina primary: 4 days

Countdown to Super Tuesday: 7 days