In general elections, the direction in which polls have moved is not predictive of the direction in which they will move.
Thus, it is usually wrong to say that a candidate is gaining ground in the polls — present tense — or that her position is improving. Instead, you should say that the candidate has gained ground or that her position has improved.
via FiveThirtyEight – The Most Overrated Concept in Elections Analysis: Momentum. Another post from FiveThirtyEight that shows why I love reading it, no spin just the facts. A sorely missing concept in reporting especially political reporting.