“So look,” the text from Page to Strzok reads, “you say we text on that phone when we talk about Hillary because it can’t be traced, you were just venting [because] you feel bad that you’re gone so much but it can’t be helped right now.”

Sen. Charles E. Grassley (R-Iowa), chairman of the Senate Judiciary Committee, wrote to Deputy Attorney General Rod J. Rosenstein demanding a fuller explanation for Page’s message, saying, “The mention of ‘Hillary’ may refer to Secretary Clinton and therefore could indicate that Mr. Strzok and Ms. Page engaged in other communications about an ongoing investigation on a different phone in an effort to prevent it from being traced.’’

People familiar with the matter said that, although Page’s message may appear to suggest that she and Strzok used a separate communications channel for discussing the Clinton case, the point of her text was to advise Strzok how to explain to his wife why the two of them had been texting each other.