Has the Republican primary fight become a two-man race, at least on a national level?  A second national poll shows Newt Gingrich and Mitt Romney tied, this time the WaPo/ABC poll, which shows them at 30% each:

Two weeks before Iowans cast the first votes of the 2012 election cycle, Republicans nationally are sharply divided over whom their party’s presidential nominee should be, with Mitt Romney and Newt Gingrich locked in a dead-even race, according to a new Washington Post-ABC News poll.

Gingrich and Romney are each favored by 30 percent of Republicans and Republican-leaning independents. Running behind them is Rep. Ron Paul (Tex.), whose libertarian philosophy has attracted a strong following. He stands at 15 percent, about double his tally in an early November poll. All other active candidates are in the single digits.

The rise of Ron Paul in this poll may have to do with the poll sample itself, which oversampled independents while undersampling Republicans.  The sample has a D/R/I of 32/25/37, in which Democrats have a +7 over Republicans and independents a +12 over the GOP.  In neither of the last two elections have independents outvoted Republicans in the exit polls.  In 2008, the D/R/I was 39/32/29, and in 2010 — the Tea Party midterms — it was 35/35/29. The poll doesn’t break down the internals for support of each candidate, but the large oversample of independents are almost certainly the main contributing factor to Paul’s performance in this poll.

Regarding Romney and Gingrich, however, the WaPo poll seems to corroborate two other polls this week.  Yesterday’s CNN poll showed Romney catching up with a still-rising Gingrich at 28%, and had Paul in third at 14%.  Gallup also shows Romney and Gingrich in a virtual tie, but calls this a “collapse,” as they had shown Gingrich far in front a couple of weeks ago:

After enjoying 14- to 15-percentage-point leads over Mitt Romney in early December, Newt Gingrich is now statistically tied with Romney in national Republican preferences for the 2012 GOP presidential nomination: 26% for Gingrich vs. 24% for Romney. This follows a steady decline in support for Gingrich in the past 10 days.

Interestingly, Gallup’s tracking poll — which polls daily, much more often than WaPo or CNN — doesn’t show any significant change in Paul’s support.  They have him at 11%, but two weeks ago he was at 10%.  On a national basis, this has become a two-man race, but Gallup’s tracking poll shows a significant opening for another candidate to change that dynamic.  The rise of both Romney and Gingrich in the other two polls make it look like that window is rapidly closing.