Why Rick Santorum or Newt Gingrich dropping out wouldn’t change much — in one chart

Depending on the results of Tuesday’s contests, there may be pressure on either Newt Gingrich or Rick Santorum to drop out of the GOP presidential race.

At which point the other one would have a good shot at beating Mitt Romney head-to-head, right?

Not exactly.

Gingrich and Santorum have been arguing for a while now that, if only the other one dropped out, they would have a good chance at uniting the conservative, anti-Romney vote and defeating the frontrunner. Santorum is expected to make this case even more vocally if he wins Missouri primary on Tuesday.

But the polling just doesn’t bear that out — at least not right now.

A new poll from the Washington Post and ABC News asks voters their second choice, giving us pretty good idea how the race would break if either Gingrich or Santorum dropped out of the race today.

And it would actually be as much or more of a boon to Romney than to the other more conservative candidate who doesn’t drop out.

The chart above shows how the initial head-to-head numbers would change, based on those second-choice answers, without Gingrich in the race, without Santorum in the race, and then without Ron Paul in the race. (Thanks to the Post’s awesome polling team for throwing together the data above.)

Romney’s lead actually expands without Gingrich in the race. While he currently holds a 23-point lead on Santorum, it would grow to 26 points.

If Santorum were to drop out, Romney would pick up about as many of his supporters as Gingrich would, and his current 16-point lead over the former House speaker would remain virtually unchanged, at 15 percent.

Romney would also pick up the biggest share of Paul’s supporters if he were to drop out of the race today, slightly expanding his 39 percent-to-23 percent lead on Gingrich to 44 percent to 26 percent.

Now, this is just a snapshot in time and isn’t the be-all, end-all. And in fact, we can see the argument behind Gingrich and Santorum wanting a straight head-to-head matchup. After all, any time you face a frontrunner, it’s best to have as few other candidates splitting up the vote and muddying the waters as possible.

But at least for now, there’s no reason to believe that Gingrich or Santorum would reap any immediate windfall from the other dropping out.