How thin is Mitt Romney's margin for error in November? Try 20 electoral votes.

The Washington Post's Chris Cillizza says Romney's ceiling for electoral votes is right around 290. Given that it takes 270 to win, that doesn't give him too many votes to play with.

That number, while it seems low, is fairly par for the course for recent Republican nominees. No Republican has received more than 300 electoral votes since George W. Bush in 1988. On the other hand, the last three Democratic presidents have gone above 365 votes.

Cillizza says Romney's path to win is extremely narrow right now.

If Romney was able to duplicate Bush’s 2000 map, he would take 285 electoral votes — thanks to redistricting gains over the past decade.

But to do so, Romney would need not only to win the five swing states mentioned above — with the exception of Missouri, all of them are considered tossups (at worst) for the president at the moment — but also hang on to states such as North Carolina and Virginia where Bush cruised 12 years ago. (Obama carried both states in 2008.)

In 2004, Bush won reelection with 286 electoral votes, losing New Hampshire from his 2000 map but adding wins in Iowa and New Mexico.

Under the 2012 map, Romney would win 292 electoral votes if he replicated the Bush 2004 victory. But New Mexico seems like a very tough place to win — not to mention the fact that he would again need to carry Ohio, Florida, Colorado and Nevada as well as North Carolina and Virginia.