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The week that could determine the GOP nominee

Republicans are voting in four states Tuesday, but next week's contests in Ohio and Florida could determine the nominee.

The Republican race for president has been upended in the last week, but the top story remains the same: If Donald Trump is not stopped in the winner-take-all states of Ohio and Florida on March 15, he will likely become the GOP nominee. At the very least, he would force an ugly contested convention at which he'd be difficult to dislodge barring a total collapse in later races. 

That makes this coming week, which includes several test races on Tuesday and a debate on Thursday before the ultimate showdown, absolutely critical. 

The biggest developments since the Super Tuesday contests on March 1, when Trump established a dominant delegate lead after winning seven states, have had less to do with Trump and more to do with his opponents. Senator Marco Rubio, who has spent the last few weeks attacking Trump as a “con artist,” appears to be sinking fast, while rivals, especially Senator Ted Cruz, steal his support.   

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Saturday’s contests in Maine, Kansas, Louisiana, and Kentucky signaled the shift. Trump won a caucus in Kentucky and primary in Louisiana, but by smaller margins than similar states like Alabama and Tennessee the week before, thanks mainly to improved performances from Cruz, who won caucuses in Maine and Kansas. Cruz’s surge came mainly at the expense of Rubio, who peaked at 17 percent support in Kansas and scraped single digits at 8 percent in Maine.

Rubio bounced back with a win in Puerto Rico the next day, but if he can’t win Florida he’ll have little rationale to stay in the race beyond the hope of influencing a contested convention.

Adding to his woes, Rubio's campaign on Monday batted down an alarming report from CNN that some campaign advisers were pushing him to exit the race before March 15, an idea campaign spokesman Alex Conant told the network was "fiction" and "not true." 

"Every day that goes by I think we're going to continue to gain votes and gain support as we get closer, but it's going to be a lot of hard work," Rubio told reporters earlier in the day in Florida. 

Michigan, Mississippi, Idaho, and Hawaii vote on Tuesday. While none of them are make-or-break contests, they offer an important heat check before Florida.

Of the four states, Michigan has the most delegates and will be watched most closely. Several polls this week showed Trump with a double-digit lead and Rubio’s support plummeting behind Cruz and Ohio Governor John Kasich, who has made the state a top target. If Trump cleans up in Michigan it could signal that his populist message is catching on in the Rust Belt, setting him up well for neighboring Ohio.

Mississippi also becomes more relevant after Saturday's races -- if Cruz overtakes Trump after losing several similar races, it might suggest Trump is hitting his ceiling as support unites against him. Cruz campaigned there on Monday, where he called Trump his “leading competitor in this state." 

While Cruz’s best natural states, namely those in the South, are mostly behind him, Rubio’s backsliding gives Cruz an increasingly strong argument that he’s the candidate best positioned to make a last stand against Trump.

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Sensing weakness, Cruz is opening offices in Florida and a super PAC supporting him announced on Monday it would run anti-Rubio ads in the state. That runs counter to the plan put forward by Mitt Romney last week to stop Trump by pushing Rubio past the finish line in Florida, and Kasich to victory in his own home state, in order to deny him a delegate majority. At the same time, major GOP donors are pouring big money -- $8.3 million so far, per NBC News – into super PACs attacking Trump, who has so far spent only $1.7 million of his own to counter them. 

A Monmouth University poll of Florida's likely voters released Monday offered mixed news for Rubio. While it put him behind Trump 38 percent to 30 percent, with Cruz back at 17 percent and Kasich at 10 percent, that was actually a significant improvement over several February polls putting Trump’s support in the mid-40s. It also showed Trump statistically tied in a head-to-head race over Rubio at 47 percent to 45 percent, however, running against hopes a narrowing field would unite the party against Trump. 

In Ohio, polls are hard to come by, but Democratic firm Public Policy Polling released a survey on Monday showing Trump barely leading Kasich 38 percent to 35 percent, with Cruz at 15 percent and Rubio at a shocking 5 percent. In an encouraging sign for Kasich, he led Trump 55-40 in a head-to-head matchup.

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The Republican field will get their best chance to make their case on March 10 in Florida, where the candidates will gather for a debate at the University of Miami. A big question will be whether the candidates maintain their recent unified response to Trump, even as Cruz eats into his support.

They’ll have plenty of ammunition to use against the front-runner: In addition to his numerous flip flops, which were thoroughly examined in last week’s debate, Yahoo published a story on Monday in which the daughter of an alleged mobster claimed her father and Trump had a close relationship despite his racist conduct in his casino, which resulted in a fine against it. So far, however, it’s not clear that the onslaught of attacks on Trump have made much difference in the last few weeks. Republicans fearful of his nomination have to hope the tipping point is within days – or else.