Senator John McCain’s momentum continues to build, with a new Washington Post-ABC News poll showing him with a commanding lead nationally amongst Republican voters.

McCain leads former Massachusetts governor Mitt Romney 48 percent to 24 percent among probable GOP voters as he continues to rapidly consolidate support, particularly among moderates and liberals. Former Arkansas governor Mike Huckabee runs third in the new poll with 16 percent, and Rep. Ron Paul (Tex.) is fourth at 7 percent.

The poll shows McCain running neck and neck with either Obama or Clinton, while both prospective Democratic nominees lead Mitt Romney by double digits.

McCain outperforms Romney in the general-election tests because he picks up significantly more support among independents and political moderates. These groups have been crucial to the senator in early-state caucuses and primaries, and his biggest gains in this poll came among them.

Among GOP voters who are politically moderate and liberal, McCain has a whopping 51-point advantage over Romney in the new poll, while conservatives divide 37 percent for McCain, 29 percent for Romney and 19 percent for Huckabee. Moreover, most of McCain’s improvement since mid-January is among moderates and liberals; he is up 28 percentage points in this group, while he and Romney have both climbed 12 points among conservatives.

In what I consider to be a real problem for Romney, McCain is now seen as best representing “core Republican values”, a test that he leads Romney in by double digits. Romney’s hopes of stopping McCain by assaulting him on the issue of being a Republican “heretic” would appear to be made much harder by that polling data. The Huckabee win in Iowa, which derailed the Romney train while McCain was at his weakest, may be the pivot point in this race for the Republican nomination. Huckabee’s continued presence in the race can only hurt Mitt. Is there a McCain-Huckabee alliance?

Read the Post story here.