If we do the math correctly, Grassley had over 40 years of time and experience in D.C. , compared to the complete absence of time of Judge from Capitol Hill. Grassley had established connections and a routine with Capital Hill decades before Judge entered the political arena.
Early on in the Iowan Democratic Senatorial Primary, Judge missed one of the last forums of the Democratic Candidates seeking nomination. The forum was considered important, but Judge would come out for the last debate and win the nomination.
As soon as the nomination was out, the National Republican Senatorial Campaign started coming after Judge specifically for her absences, even connecting her absences as "brown-nosing" the Democrats of Washington D.C.
Grant it, Grassley had some leg to stand on, especially considering he had broken the record for most consecutive (not missed) votes while in office. But one cannot forget the fact that Grassley already had the most years of experience in D.C.
How It relates to gendered politics
Needless to say, it always proves to be difficult for an incumbent to lose their seat in an election due to the popularity of their name. The incumbent's experience also doesn't help their opponent in claiming that they have more of a standing. However, for Grassley and the NRSC, they approached their attacks on Judge from a different angle.
Special requirements are often considered essential when it comes for a woman to run. “A woman is confronted with special requirements and problems… Women candidates and partisans may find these specific requirements objectionable and onerous, but they are real; they must be dealt with in the course of a successful campaign” (Kirkpatrick 1972, 99). Often times, their competence and familiarity with the system are used against them.
We see Judge's trips to D.C. as a source of attack, not as an argument for her to be the Senator. We also see that her competence of being her own mind and representing the people of Iowa is challenged, claiming that her D.C. trips make her an insider and just a feed for Senator Harry Reid and President Obama. Her femininity or family weren't called into question, but this double standard while Judge was running against a deeply entrenched D.C. Republican who himself probably adheres to the party (as displayed by his endorsement of Trump) only goes to show that even the right qualifications for a woman don't meet up to standards, evidenced by her stark loss to Grassley by over 20 points.
Source: NY Times ( http://www.nytimes.com/elections/results/iowa-senate-grassley-judge )
Though politicians may or may not have loaded language or blatant remarks gendered conversation or prejudices, the Iowan Senatorial race displayed strategically subtle implementations of gendered strategy. Grassley's manner in attacking the qualifications of Judge that would have normally been praised revealed the double standard in treating male vs. female candidates. Grassley and the Republicans took advantage of their opponent and changed the rules so that the being an outsider is a negative instead of the positive, demonstrating that gender progress in electoral politics still has a long way to go.