March 9th update: Donald Trump finished first in the Michigan primary, where candidates' percentages closely tracked the Monmouth poll -- Trump earning 37% of the Republican primary vote, Ted Cruz 25%, John Kasich 24% and a fading Marco Rubio with 9%. Yet, consistent with Monmouth's head-to-head polling, a CBS News exit survey showed that Cruz would have edged Trump head-to-head. (Trump leads Rubio, and there was no query about Trump vs. Kasich). ABC news exit polls had similar findings, and found that Cruz even would have come close to catching up in Mississippi, where Trump had 47% of the vote.

Nationally, a March 8 NBC poll reported a narrower Trump plurality vote lead than other polls (30% for Trump to 27% for Cruz, 22% for Kasich and 20% for Rubio), but more instructively, showed the same pattern of Trump's ceiling of support, with Trump trailing head-to-head to Kasich (57% to 40%), Cruz (57% to 40%) and Rubio (56% to 43%).

The Republican Party has a problem in its presidential nomination process. As it turns toward holding winner-take-all contests on March 15, including in the delegate-rich states of Florida and Ohio, its use of a plurality voting system may well allow a candidate to win the nomination who would be unlikely to win in a head-to-head contest with his strongest opponent.

Businessman Donald Trump is the current beneficiary of facing several challengers who divide the majority vote. FairVote has explored this vote-fracturing in detail over the past months -- in a series of blogs on polls that asked head-to-head questions as early as November, in our report of our national poll of Republican and independent voters in partnership with the College of William and Mary, and in recent analyses of all head-to-head polls and our simulation of how ranked choice voting would likely have played out if used in South Carolina and the Super Tuesday primaries.

This week we have seen an important new national poll from the Washington Post and ABC, and state polls from Ohio that tell the same story.

National Poll from ABC News/Washington Post: The ABC coverage of its new national poll released Tuesday shows Trump ahead with 34 percent, followed by Ted Cruz with 25 percent, Marco Rubio with 18 percent, and John Kasich with 13 percent. But, as ABC reports, "in hypothetical two-way matchups, Cruz leads Trump by 54-41 percent and Rubio leads Trump by 51-45 percent in this poll." In other words, in an instant runoff tally, Cruz would pick up 29% between the first round and final head-to-head with Trump, while Trump would gain only 7%. The ABC story reports on various voter breakdowns of the head-to-head choice in a helpful way.

Michigan Poll from Monmouth University: Michigan held its primary Tuesday, using proportional allocation of delegates. Released Monday, a Monmouth University poll of Michigan voters found that 36% supported Trump, followed by Cruz (23%), Kasich (21%) and Rubio (13%). But again, head-to-head, the numbers would be very different. Ted Cruz would have defeated Trump 48% to 41%, and even Rubio would have come back from trailing 36% to 13% to lead 46% to 45%.

Ohio Poll from Public Policy Polling: Turning to next week's winner-take-all contest in Ohio, the new Public Policy Poll shows that Trump leads with 38% over Kasich (35%), Cruz (15%), and Rubio (5%), with 31% saying they might change their minds. Kasich, who is governor of Ohio and has by far the highest approval rating in the state of any of the candidates, moves far head of Trump head-to-head, 55% to 40%. Public Policy Polling reports that "Rubio voters move to Kasich 75/16 over Trump, Cruz voters do so 69/25, and undecideds would pick him 54/11 if Kasich and Trump ended up being the two candidates they chose."

Florida Poll from Monmouth University: Another key winner-take-all state next week is Florida. Monmouth's new poll shows that Trump both leads in the plurality vote and might well win head-to-head contests in the state. His first round lead is narrower in this poll than in some other recent Florida polls, with a 38% to 30% for Rubio, 17% for Cruz and 10% for Kasich, but he holds on to lead narrowly against Rubio (47% to 45%) and more strongly against Cruz (48% to 40%). Nearly a fifth of Florida Republicans reported already voting early. (As an aside, Monmouth made use of a ranked choice vote in its polling, reporting that "[Ben] Carson’s name was included in the list read to voters on Thursday only. His support from that night was re-assigned to voters’ second choice.")

The bottom line is that Donald Trump continues to be well-positioned to win states if the field does not narrow or does not consolidate around one candidate. Without ranked choice voting, winning 35 percent of the vote might well be enough.

Editor's note: This article, written by Rob Richie, originally published on FairVote's blog on March 8, 2016, was updated on March 9, and has been slightly modified for publication on IVN.