Washington CNN  — 

The American Health Care Act is out of the House. The action now moves to the Senate, where President Donald Trump’s attempt to overhaul the health care system faces a far more perilous fate.

The focus will be almost entirely on the Republican side as Senate Majority Leader Mitch McConnell tries to craft a bill that can win the votes of 50 of the 52 GOPers. (It’s hard to see – at least right now – any Democrat voting for any sort of health care bill.)

Each one of those 52 is, obviously, important. But some are more important than others. Below is my list of the seven senators to watch, the people who are likely to not only be front and center on the bill over the next few weeks but could well hold its fate in their hands.

1. Lamar(!) Alexander

 Sen. Lamar Alexander of Tennessee speaks to reporters on Capitol Hill in 2013.

Alexander is important for three reasons: He’s the chairman of the Senate Health, Education, Labor and Pensions (HELP) Committee, he’s from a state that would be heavily impacted by the changes made to the pre-existing conditions mandate in the House bill and he’s someone well positioned, as a former member of party leadership, to bring warring factions within the GOP conference together.

“The Senate will now finish work on our bill, but will take the time to get it right,” Alexander said in a statement released Thursday. And, as a smart GOP Senate insider pointed out to me, Republicans have been listening to Lamar on health care since the big 2010 meeting with then-President Obama at Blair House.

2, 3, 4. Susan Collins/Lisa Murkowski/Rob Portman

Healthcare Tuesday 9p
Senator snaps at reporter asking about bill
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Each of these less ideologically driven senators have already voiced concerns over the House bill, most notably its provision to freeze Medicaid expansion funds in 2020. Murkowski, in particular, offered a decidedly circumspect view of what the House passed Thursday.

“I think you will see an effort coming out of the Senate that will be separate from what the House has done,” she told the Fairbanks Daily News-Miner (amazing name!) on Thursday night. “Incorporating what aspects of the House bill remains to be seen.”

Another complicating factor: Collins is currently considering a run for governor in 2018. Maine, under Gov. Paul LePage, rejected the federal Medicaid expansion and LePage has vetoed attempts by the Democratic legislature to opt into the system.

5. Ted Cruz

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Cruz, Sanders debate Obamacare in 90 seconds
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Remember that the Texas senator and runner-up in the 2016 presidential primary fight was the lead agitator in shutting the government down in 2013 over funding for Obamacare. This could be a return engagement for the still-ambitious Cruz, who may see an opportunity to further bolster his national credentials by positioning himself as the uncompromising voice of the base on the bill.

Is full repeal – a total non-starter for a handful of Cruz’s Republican colleagues – the only path to success in his mind? “We’ve been promising the voters we’d repeal Obamacare for seven years, and I think if we fail to deliver on that, I think, the consequences would be catastrophic,” Cruz told a San Antonio radio station Thursday.

6. Dean Heller

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Crowd angrily chants 'yes or no' at senator
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Heller is the only Republican Senator up for re-election in 2018 in a state – Nevada – that Hillary Clinton won in 2016. That means protecting him from any career-killing votes will be a priority for McConnell. “I will not support it in its current form in the Senate, and am confident that what the Senate considers and approves will be different from the House bill,” Heller said of the bill after the House vote. He expressed significant concern with the freezing of Medicaid funds and the abolishing of the pre-existing conditions mandate.

7. Rand Paul

Rand Paul FreedomWorks
Sen. Paul proposes insurance through the NRA
01:46 - Source: CNN

Paul, like Cruz, made a national name for himself with his opposition to the ACA. And he’s shown a bit of a penchant for grandstanding already this year when he waited outside the closed doors of the room where House Republicans were writing the bill. Paul’s position is made more complicated by his alliance with his home state colleague McConnell. How far is Paul willing to push? And how much influence – if any – does McConnell have over him?