Buying a word like “impeachment,” and landing as the first result, does not come cheaply. Google’s search advertising business functions as an auction, so the more popular a search term is, the more expensive the ad will be while the word is popular. For example, advertising under any iteration of the phrase “Super Bowl” will be exceptionally expensive on the day of the game, though relatively inexpensive in mid-July.

Sign up for On Politics to get the latest election and politics news and insights. Sign up for our politics newsletter

“I would think that, if you truly wanted to own impeachment as a search term, it would be hundreds of thousands of dollars per day,” said Ryan Meerstein, a managing partner at Targeted Victory, a Republican digital consulting firm.

Google’s transparency report does not include which words or phrases a campaign is advertising around, so it is impossible to know how much Mr. Bloomberg is spending on the impeachment ad, or where his campaign may be targeting the ad based on demographics or geography.

Other campaigns and political entities are currently running ads against the word “impeachment,” though not in the prized first-page position. Users clicking to the second page of search results would occasionally see an ad from the Cato Institute, the libertarian think tank, offering its opinion of impeachment as defined by the Constitution. On the third page on Monday was an ad from Representative Abigail Spanberger, a freshman Democrat who has been targeted by Republicans for her support of impeachment.

For political campaigns, Google ad searches are particularly effective at “acquisition,” the political operative’s term for either obtaining some type of personal contact information or, more important, luring in small-dollar donations. In this primary cycle, as Democratic candidates have had to acquire hundreds of thousands of individual donors to qualify for the debate stage, Google word-search ads have been particularly essential. (Mr. Bloomberg, however, has said he is not soliciting individual donations.)

They can also be an essential tool around particular moments in a campaign, such as a debate or some viral news cycle. Mr. Meerstein noted that political campaigns see a huge spike in search interest during the final weekend before a state primary.