The U.S. Senate voted Thursday to change the rules governing filibuster. The largely party-line vote removed the minority party’s ability to block most presidential nominations, though it will still be able to do so on Supreme Court nominations.

The change has been described as the “nuclear option,” and with good reason. For more than 200 years it has taken a supermajority — generally two-thirds of the Senate — to expel a senator, approve a treaty, impeach a president, override a presidential veto or amend the Constitution. Then, in 1975, the Senate set up new rules for the cloture votes that end debate on a measure, requiring that 60 members vote in favor.

Now, it will take only a simple majority to end that debate.

It may not sound like a big deal, but it is. The Senate is far different from the U.S. House of Representatives or at least it claims to be. Its members serve six-year terms, with roughly one-third being elected every two years.

It has been called the “cooling saucer” of the national legislature, a place where proposed laws have time to rest as nerves and public opinion settle. The old filibuster rules enhanced that cooling effect.

But just as the U.S. House of Representatives has grown nearly unworkable in the last few years, so, too, has the Senate struggled, and the filibuster has in some ways made its problems worse.

Consider this: In 1960, only 8 percent of bills in the Senate were subject to filibuster; today, that number is 70 percent. Viewed that way, and ignoring the politics of the situation, Thursday’s vote makes sense.

Yet it will almost certainly come back to haunt Senate Democrats in ways they should have foreseen. The filibuster is a safeguard for the minority party; now that safeguard is gone. Democrats don’t have to worry about that now, but they will not be in the majority forever — no doubt a reality the three Democrats who voted against the change were well aware of.

Already, in fact, Republican Sen. Charles Grassley, of Iowa, has laid out clearly what is at stake. Without the 60-vote rule, it would be a simple matter for a Republican-controlled Senate to change the rules again, giving to themselves the power to veto a Democratically appointed Supreme Court nominee by just one vote. If that happens, the cooling saucer, now cracked, may shatter.