From a longer article that this article was sourced from:
Presidents Bush took the “easy way out” by picking Souter and Roberts, Cruz said. “They didn't want to spend the political capital trying to confirm a proven conservative.” As examples of principled conservative justices he'd model his nominees after, Cruz cited Scalia, Clarence Thomas, William Rehnquist, and Samuel Alito.
http://www.bloomberg.com/politics/articles/2015-12-02/ted-cruz-vows-to-put-hard-core-conservatives-on-the-supreme-court
So there he uses the phrase again. It still doesn't tell me what he means by "spend the capital". It must mean something, or he could have just left it at saying he'd appoint proven conservatives.