Harry Reid's decision to retire rather than seek reelection in 2016 is important for the future of the US Senate. It is plausible, though not exactly likely, that Democrats could secure a Senate majority given the relatively friendly electoral map of 2016. A senior incumbent in a purple state retiring makes it harder. But Reid is not just a senior senator — he's the leader of the Democratic Party caucus, and has been for some time. When he steps down, he'll be replaced by a new leader with a different political record and a different policy agenda.
By most accounts, New York's Chuck Schumer is the most likely contender to succeed Reid. Illinois's Dick Durbin, the current number two in the caucus hierarchy, is also a very plausible candidate. Less plausibly, there are liberals talking about Elizabeth Warren.
Yet to a surprising extent, this won't make much of a difference. Legislative leaders are important people. But especially in the US Senate, leadership is more like being captain of a rec league basketball team than like being a coach in the NCAA tournament. You can only lead the caucus in directions the members are willing to follow, and the imperatives of doing the job often mean the leader's priorities change as much — if not more so — than the party's.
Harry Reid was pro-life, until he was in charge
Reid himself is an excellent exemplar of these trends. As a Mormon and a Nevadan, Reid had a number of distinctive policy positions in the 1980s and 1990s that separated him from the average Democrat. At times, these idiosyncratic stances lined up well with the larger demographic and ideological trends in American life. As leader, Reid ended up championing immigration reform and solar power — two issues whose salience was unusually high in his home state but that aligned well with the overall trajectory of the Obama-era Democratic Party.
But early in his career, Reid also stood out as an advocate of conservative views on abortion and gun rights. In 1998, he said abortion should be illegal except "when the pregnancy resulted from incest, rape, or when the life of the woman is endangered."
Yet he was also a loyal partisan Democrat. He voted to confirm Bill Clinton's judicial nominees and to oppose George W. Bush's. He voted for Democratic budgets and against Republican ones. By the time he took over as Democratic leader in 2005, it was clear he wasn't pro-life in any real operational sense. He wasn't using his position in the leadership to push for votes on anti-abortion bills or in any way advance the anti-abortion agenda. After all, if he'd done that, he'd have been deposed. The Democratic Party is firmly pro-choice and the GOP firmly pro-life, and nobody can exercise leadership in either party without conforming to this.
More recently, Reid's long tenure in leadership caused his views to completely merge with those of the larger party. His communications and fundraising teams were, necessarily, doing communications and finance work on behalf of the entire party. In January of this year, a fundraising email went out under Reid's name raising the alarm about the anti-abortion tilt of the new majority:
We knew it would be bad, Friends – but this Republican Congress surpassed our WORST NIGHTMARE:
On DAY ONE, Republican extremists in Congress launched their first major assault on women’s health care – pushing a bill that would have BANNED abortions after 20 weeks of pregnancy.
One could call it hypocrisy, but it's bigger than that. The caucus leader reflects the caucus's view, and that's true no matter who holds the office.
The next leader matters — but not for policy
There are real differences between Schumer and Reid. As a New York legislator, Schumer takes a kinder view of Wall Street as something of a hometown industry. He also is a genuinely passionate and fired-up hawk on Israel-related issues. But it would be a mistake to think his ascension would lead to a massive Democratic Party reorientation in favor of Bibi Netanyahu and Jamie Dimon. If anything, the opposite. If he becomes leader, Schumer will have to sand down the edges of his personal approach to politics in order to better fit the posture of generic Democratic leader. This is one reason the Warren idea is so ridiculous — if your passion in life is picking intra-party fights, a leadership job would be a disaster.
Precisely because the new leader will back the caucus's policy agenda regardless of who the new leader is, policy ideas likely won't loom large in the fight. Democratic senators want a leader who can do a good job of fundraising, a good job of message coordination, and a good job of representing the caucus's views in talks with the House and the White House. This is harder for outsiders to evaluate than policy positions, but much more important to actual senators.