The site is like a 1995 Ford Escort with a 500-horsepower advertising engine under the hood.

– Alexis Madrigal, senior editor at The Atlantic, describing the Drudge Report in an article entitled “Drudge Report Looks Old-School, but Its Ad Targeting Is State-of-the-Art”

In February, for the first time ever, Arianna Huffington’s liberal political mega-blog and news site, the Huffington Post, has apparently surpassed the longtime mighty blog leader, Matt Drudge of the conservative/populist-leaning Drudge Report, according to recent traffic data reports from both comScore (SCOR) and Nielsen Online. (Both are pictured here.)

According to data from Nielsen Online, for example, the Huffington Post’s traffic–as measured by monthly unique visitors in the U.S., at home and work–has more than tripled since February of 2007, when it had about 1.1 million unique visitors; by February of 2008, unique visitors had risen to 3.7 million.

In that same month, the Drudge Report had 3.4 million (it had 2.75 million in February of 2007).

Data from comScore is different, as measurement data often is, but shows the same trend (see chart below). The Huffington Post jumped from 457,000 unique visitors in the U.S. at all locations, but had risen to 2.3 million in February of 2008.

For Drudge, comScore reported that it had 1.2 million unique visitors in February of 2007 and 1.6 million in February of 2008.

Of course, internal logs at both sites are likely to show much higher numbers than either comScore or Nielsen Online, by a factor of even four or five times.

Sources at the Huffington Post, for example, said that logs show 12 million uniques for the last month, which they attribute to the addition of new vertical sites within the main site, as well as an increased interest in political news and analysis.

In comparison, Drudge’s site notes it had 21.8 million visits in the past 24 hours. But the site does not define this figure, and it is not and cannot be compared to unique visitors.

“We couldn’t be more pleased with our traffic growth and look forward to continuing to build out our brand,” wrote Arianna Huffington in an email, asking about the traffic spike on her site.

(BoomTown sent an email to the Drudge Report’s contact email on its site late last night, asking for a comment about the data, and will post a reply if I receive one.)