So far, the speech delivered by First Lady Michelle Obama has been more widely viewed online than any other speech at this week’s Democratic National Convention, according to Visible Measures Corp., a digital video analytics company based in Boston.

With more than 2.5 million views, Michelle Obama’s speech got roughly 1 million more views than the speech given by former President Bill Clinton. As of Friday morning, President Obama’s Thursday night speech had generated about 308,000 views.

Because the speeches were delivered on different nights, it’s hard to generate apples-to-apples comparisons at this point. Visible Measure plans to issue a follow-up report next week.

The most widely viewed convention speech so far was given last week by actor Clint Eastwood at the Republican convention. To date, Eastwood’s speech has been viewed online 5.7 million times, Visible Measures said.

To calculate viewership, Visible Measures says it uses something called True Reach methodology. The methodology “combines the performance of video clips related to an event, from the original event, to copies of the event, to mixes, mashups, parodies, satires, commentaries, and more,” the firm said. “This provides us with a holistic view of true performance of video online.”

In Michelle Obama’s case, her speech has inspired more than 60 video clips across the Web, from snippets highlighting certain lines of the speech to the complete 25-minute version, the firm said. After 72 hours, Ann Romney’s speech had generated 383,000 video views online.

To date, the speech given by Republican presidential candidate Mitt Romney has driven 336,000 views, Visible Measures said.

If online viewership of speeches is any guide, San Antonio Mayor Julian Castro was the “surprise breakout star” of the Democratic convention, according to Visible Measures. Castro’s speech has generated more than 460,000 views to date.

So far, Governor Deval Patrick’s speech has been viewed online nearly 107,000 times. So far, the speech given Elizabeth Warren, the Democratic candidate for a Massachusetts US Senate seat, has been viewed nearly 92,000 times, Visible Measures said.

Last month, Visible Measures announced that it had secured $21.5 million in additional funding in a round led by DAG Ventures. Founded in 2005, Visible Measures has raised more than $65 million to date. Clients include consumer-products giant Procter & Gamble Co., Ford Motor Co., and technology giant Microsoft Corp.