lock up

Hello.

I have difficulty in understanding the sentence below, especially the underlined part.
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In the spring of 1992, Bill Clinton .

I guess it means he was nominated as a candidate of the Democratic party. (Bill locked up the door to the nomination, so other candidates failed to open the door.) Am I right?

I really need your help.
Thank you in advance!

"Locked up" here is a metaphor for "secured."

Bill Clinton had not been nominated at that point, but he had secured enough delegates (through the caucus and primary election processes) that his nomination was certain.

Florentia52 said:

"Locked up" here is a metaphor for "secured."

Bill Clinton had not been nominated at that point, but he had secured enough delegates (through the caucus and primary election processes) that his nomination was certain.

Thank you! Great help!