Why US Senators obstruct some executive agency nominations over others

The average delay between an executive nomination and confirmation by the US Senate is 120 days, but some nominees can experience delays of more than 400 or 500 days. In new research which examines over 8,000 bureaucratic nominations over 25 years, Ian Ostrander finds that nominations are targeted for delay based on their policy value, public importance, and the perceived ideology of the agency in question. For example, important agencies with low public importance, such as the Federal Election Commission, are often targeted by Senators for nomination delays