The Senate on Wednesday confirmed Tulsi Gabbard to be the next director of national intelligence in a 52 to 48 vote that demonstrated President Trump’s political control over Republican lawmakers.

Ms. Gabbard had one of the most contentious confirmation hearings of all of the president’s nominees. A number of Republican senators joined Democrats in asking tough questions about her previous support of Edward Snowden, a former government contractor who released reams of classified data, and her skepticism about warrantless wiretaps of overseas communications.

Her defense of Bashar al-Assad, the former Syrian dictator, and her sympathy toward President Vladimir V. Putin of Russia also gave some Republican lawmakers pause.

But in the end only one Republican was willing to oppose her. Senator Mitch McConnell, Republican of Kentucky and the former majority leader, voted against her. Mr. McConnell has taken stances against several of Mr. Trump’s nominees, but so far has not persuaded many in his caucus to join him.

Before the floor vote, the Republican members of the Senate Intelligence Committee fell in line and backed Ms. Gabbard’s confirmation. Some, like Senator Susan Collins of Maine, highlighted Ms. Gabbard’s pledges to streamline the office. Others, like Senator Todd Young of Indiana, emphasized her vows to hold accountable people who leaked classified information and to help reauthorize overseas surveillance programs.

That support from skeptics paved the way for Ms. Gabbard’s confirmation by the full Senate.

Democrats remained united against her. Senator Chuck Schumer of New York, the minority leader, said Ms. Gabbard was not qualified. He said that in a secret vote, she would have received little Republican support. He said he was troubled by her “long record of weakness” against Russia.