Pirro is way out of her element. Not only does she have major baggage, she is almost uniformally wrong on issues of conscience, reflecting the very worst of what we know RINOs to be. Although I wouldn't be thrilled, I might've been persuaded to support her for Attorney-General, but the Senate seat is a non-starter.
As for former Mayor Spencer, I believe he has demonstrated he is clearly the best of the potential candidates. He not only served with distinction as Mayor, he also managed the very anti-RINOesque task of passing off his job to another Republican (and not through resignation). Even saying that, I think Hillary has a cloak of invincibility and short of putting Giuliani up against her, there may be no one that can take her down (and that speaks more to the utter stupidity of NY state voters than anything else, allowing a criminal demogogue to ascend to the highest levels of power). At best, we can only hope to inflict considerable damage to her (short of beating her), but we won't accomplish by running a pot-calling-the-kettle-black RINO.
"and that speaks more to the utter stupidity of NY state voters than anything else"
The New York GOP has a lot to answer for, but no one would have defeated Hillary Clinton in 2000. Al Gore won the state by 1.7 million votes that year. In addition, demographics don't favor Republicans in NY. People drawn to life in NYC aren't known for their conservativism. It's not as if the GOP can force voters to support them against their will.
Mayor Spencer sounds like a much better candidate than Pirro. If he could get elected and reelected in Yonkers, he might not do so poorly in Brooklyn and Queens and should do well in Staten Island, Long Island and parts of Westchester. He'd have to build up his name ID bigtime in Upstate if he is to make a real race out of it, but I don't think his issue positions would hurt him Upstate (as would be the case with Pirro).
One guy I thought might make a good challenger to Hillary was former Congressman Jack Quinn of Buffalo, whose only flaws as a statewide candidate would be (i) his potential inability to connect with NYC metro area voters and (ii) his apparent lack of interest in reentering the political fold. Spencer sounds like someone similar to Quinn in his conservative stances on social issues and ability to win in a heavily Democrat area.
Of course, as much as I hate to say this, our best shot at beating Hillary might actually be George Pataki (who has recovered from low poll ratings several times during his 11 years as governor). But he wants to run for President (snicker).