WaPo acknowledges that there is vote fraud that can effect an election and that they're just okay with it.

Could non-citizens decide the November election?

You can read the whole piece by following the link above. 

"Our data comes from the Cooperative Congressional Election Study(CCES). Its large number of observations (32,800 in 2008 and 55,400 in 2010) provide sufficient samples of the non-immigrant sub-population, with 339 non-citizen respondents in 2008 and 489 in 2010. For the 2008 CCES, we also attempted to match respondents to voter files so that we could verify whether they actually voted.

How many non-citizens participate in U.S. elections? More than 14 percent of non-citizens in both the 2008 and 2010 samples indicated that they were registered to vote. Furthermore, some of these non-citizens voted. Our best guess, based upon extrapolations from the portion of the sample with a verified vote, is that 6.4 percent of non-citizens voted in 2008 and 2.2 percent of non-citizens voted in 2010.

Estimated Voter Turnout by Non-Citizens
	2008	2010
Self reported and/or verified	38 (11.3%)	13 (3.5%)
Self reported and verified	5 (1.5%)	N.A.
Adjusted estimate	21 (6.4%)	8 (2.2%)

Because non-citizens tended to favor Democrats (Obama won more than 80 percent of the votes of non-citizens in the 2008 CCES sample), we find that this participation was large enough to plausibly account for Democratic victories in a few close elections. Non-citizen votes could have given Senate Democrats the pivotal 60th vote needed to overcome filibusters in order to pass health-care reform and other Obama administration priorities in the 111th Congress. Sen. Al Franken (D-Minn.) won election in 2008 with a victory margin of 312 votes. Votes cast by just 0.65 percent of Minnesota non-citizens could account for this margin. It is also possible that non-citizen votes were responsible for Obama’s 2008 victory in North Carolina. Obama won the state by 14,177 votes, so a turnout by 5.1 percent of North Carolina’s adult non-citizens would have provided this victory margin."

.....

"We also find that one of the favorite policies advocated by conservatives to prevent voter fraud appears strikingly ineffective. Nearly three quarters of the non-citizens who indicated they were asked to provide photo identification at the polls claimed to have subsequently voted."

The dismissive tone of this paragraph says a lot about the mindset of these people. It's not the back handed slam on conservatives. It's the fact that they never consider that there may be and should be effective controls on voting. So, if ID's are ineffective, they are probably quite happy. Remember, when everybody is citizen then nobody is a citizen. 

What the first paragraph shows is that even  a small amount of vote fraud can have a dramatic impact on the vote.