Pew Research, Gallup, The New York Times and CBS, and a gaggle of others now have the GOP contest a toss-up between Mitt Romney and Rick Santorum, with sagging numbers for Newt Gingrich and Ron Paul.

But beyond the current national snapshot, the trends over the past few weeks are dramatic. First, Santorum’s recent surge has been across the board, while Gingrich’s parallel fade has been equally steep, in almost all groups. Romney’s path from the first primaries through this past weekend has been consistently rocky.

A look at Gallup tracking data since the start of the year tells the tale. (Gallup releases demographic data weekly, so the latest update doesn’t include the past two nights of interviews, where Santorum’s rise continued.) The chart below breaks out the trend, by group.

Some highlights that may not be new, but are starkly portrayed on the chart (click here for larger version):

GOP primary data (Jon Cohen/The Washington Post)

— Santorum’s rise is consistent across the board, with his support peaking among weekly churchgoers and conservatives. He’s also had a big run-up in the Midwest, paralleling his improved standing in recent Michigan polls.

— Gingrich’s support rose sharply leading into the Florida primary, but sunk just as quickly afterward. This is also true in the South, where the former House speaker has pinned his hopes.

— Romney has had a choppy run, but after Florida had a bump up in support among those with family incomes of $90,000 and up. He also pretty consistently does better out West than elsewhere.

— Paul’s support has ticked down in all groups, including some of his best. He continues to do far better among younger than older voters, but even among those under 35 years old, his numbers are on a downward trajectory. There’s a similar trend among GOP-leaning independents.

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