Tied up in Michigan: New NBC/Marist poll -- Romney 37%, Santorum 35%, Paul 13%, Gingrich 8%... But NBC/Marist also has Romney with a sizable lead in Arizona – Romney 43%, Santorum 27%, Gingrich 16%, Paul 11%... Organization is helping Romney in both states (see his early-voting/absentee advantage), but ideology is hurting him (Tea Party supporters and conservatives breaking toward Santorum)… General-election numbers: Obama leads in Michigan, but trails in Arizona… Three questions heading into tonight’s GOP debate in Arizona… It’s the 20^th of the cycle, and it begins at 8:00 pm ET… And Obama’s corporate-tax plan.

*** Tied up in Michigan: Less than a week before Tuesday’s crucial GOP presidential primary in Michigan -- and before tonight’s debate in Arizona -- a new NBC/Marist poll finds Mitt Romney and Rick Santorum locked in a statistical tie in Michigan, while a separate NBC/Marist survey shows Romney comfortably leading in Arizona. The Michigan numbers among likely Republican primary voters: Romney 37%, Santorum 35%, Paul 13%, and Gingrich 8%. The Arizona figures: Romney 43%, Santorum 27%, Gingrich 16%, and Paul 11%. “Michigan is neck and neck,” says pollster Lee Miringoff, director of the Marist College Institute for Public Opinion, which conducted both surveys (Feb. 19-20).

Paul Sancya / AP, file

A new NBC/Marist poll finds Mitt Romney and Rick Santorum locked in a statistical tie in Michigan, while a separate NBC/Marist survey shows Romney comfortably leading in Arizona.

*** Organization vs. momentum: What’s helping Romney in both states is organization; what’s hurting him is a lack of support from conservatives. Among those who have ALREADY voted absentee in Michigan -- 16% of likely GOP voters, according to the poll -- Romney leads Santorum, 49%-26%.But among those who HAVEN’T voted in Michigan yet, Santorum is up by one point, 37%-36%. The same is true in Arizona: Among those who have voted early or absentee in Arizona -- more than half of all likely GOP voters in the poll -- Romney leads by 30 points, 52%-22%. But his lead is just one point among those who haven’t voted yet, 34%-33%. Call it organization vs. momentum. But while the Romney campaign’s early-voting organization is clearly helping him, a lack of support from conservatives is hurting him. In Michigan, Santorum leads Romney among self-identified Tea Party supporters, 48%-29%, and those who describe themselves as “very conservative,” 59%-20%. Yet among those who don’t support the Tea Party, Romney is ahead by more than 20 points, 45%-24%. The same ideological pattern is true in Arizona, although Romney performs much better with the most conservative voters there than in Michigan (thanks in part to the larger Mormon population in Arizona).

*** Obama leads in Michigan, trails in Arizona: Turning to the general-election race in November, Obama leads Romney in Michigan by nearly 20 points among registered voters, 51%-33%, with 15% undecided. Against Paul, the president’s lead is 22 points (53%-31%); against Santorum, it’s 26 points (55%-29%); and against Gingrich, it’s 28 points (56%-28%). What’s more, 51% of registered Michigan voters approve of Obama’s job; 63% of them believe the auto industry bailout was a good idea (including 61% of independents and 42% of likely GOP primary voters); and a majority think the president deserves credit for the auto industry’s recovery. But Arizona is tougher territory for the president, whose approval rating among registered voters in the state is just 38 percent. In hypothetical match-ups in the state, Obama trails Romney by five points (40%-45%); Santorum by three (42%-45%); Paul by two points (41%- 43%); yet he leads Gingrich by five (45%-40%). Bottom line: Michigan probably won’t be a battleground come November, and Arizona also appears to be a reach -- though the one number Team Obama might take heart in is the fact he ONLY leads Romney 50%-33% among Hispanics in the state… with 17% undecided. But it’s still hard to see how the president gets over 47%-48% in Arizona THIS November.

*** Three questions heading into tonight’s debate: The four remaining Republican presidential candidates will gather tonight in Mesa, AZ beginning at 8:00 pm ET to participate in the 20^th debate of the GOP race. Here are three questions we have going into the debate. One, will Santorum get sucked into the conversations on social issues? Over the past four or five days, the story surrounding Santorum has been defined by either religion or social issues. (The latest development here: The Drudge oppo-research hit on a 2008 Santorum speech in which Santorum said, “Satan is attacking the great institutions of America.”) Two, will the debate feature the emerging “bro-mance” between Romney and Paul? (The latest examples: Paul’s new TV ad hitting Santorum, as well as his campaign sending anti-Santorum oppo to reporters.) And three, after being largely silent over the last couple of weeks, will we see any life from Gingrich tonight?

*** On the trail, per NBC’s Adam Perez: Before tonight’s debate, Romney holds a rally in Chandler, AZ… And Santorum delivers a speech in Tucson.

*** Obama’s corporate-tax plan: “President Obama will ask Congress to scrub the corporate tax code of dozens of loopholes and subsidies to reduce the top rate to 28 percent, down from 35 percent, while giving preferences to manufacturers that would set their maximum effective rate at 25 percent,” the New York Times writes. Treasury Secretary Tim Geithner will outline this corporate-tax plan today. A couple of points to make here: 1) The White House is refusing -- for now -- to get into individual income-tax reform, because that’s MUCH trickier (you have to eliminate popular deductions, etc.); and 2) The timing of this announcement comes before Romney’s own economic speech on Friday. As NBC’s Garrett Haake reported yesterday, Romney promised “to unveil a more specific economic plan later this week, one that that would integrate his views on tax policy, spending and entitlement reform into one complete package.” It is hard to do corporate tax reform separate from individual income tax reform which is why this White House policy release should be viewed through a much more political prism until and unless we see real details on individual income tax reform.

Countdown to Arizona and Michigan primaries: 6 days
Countdown to Super Tuesday: 13 days
Countdown to Election Day: 258 days

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